2. What is DNA Polymerase
DNA Polymerases are a group of
enzymes that catalyse the synthesis of
DNA during replication.
The main function of DNA
polymerases is to duplicate the DNA content
of a cell during cell division.
3.
4. History
Arthur Kornberg purified and characterized DNA
polymerase from E.coli for the first time.
It is a single-chain polypeptide now known as DNA
polymerase-I.
Scientists have now found five DNA polymerases
in E. coli.
5. Prokaryotic DNA Polymerase
Types and Function
There are five DNA polymerases identified in E.coli.
That is…
DNA polymerase I
DNA polymerase II
DNA polymerase III
DNA polymerase IV
DNA polymerase V
6. DNA polymerase
DNA polymerase I
It is a single polypeptide and has a role in
recombination and repair.
It has both 5’→3’ and 3’→5’ exonuclease
activity.
It removes the RNA primer from lagging strand
by 5’→3’ exonuclease activity and also fills the gap.
7. DNA polymerase II
It is made up of 7 subunits.
Its main role is in repair and also a backup of DNA
polymerase III.
It has 3’→5’ exonuclease activity
8. DNA polymerase III
This is the main enzyme for replication in E.coli. It is
coded by polC gene.
The polymerization and processivity rate is maximum
in DNA polymerase III.
It also has proofreading 3’→5’ exonuclease activity.
DNA polymerase III of E.coli is made up of a total of 13
subunits
9. DNA polymerase IV
Its main role is in DNA repair during SOS response,
when DNA replication is started at the replication
fork.
DNA polymerase II, IV and V are translesion
polymerases
10. DNA polymerase V
DNA Polymerase V is also involved in translesion
synthesis during SOS response and DNA repair
11. Eukaryotic DNA Polymerase
Like prokaryotic cells, eukaryotic cells also have many
DNA polymerases, which perform different functions,
e.g. mitochondrial DNA replication, nuclear DNA
replication, etc.
The nuclear DNA replication is mainly done by DNA
polymerase 𝝳 and 𝜶.
There are at least 15 DNA polymerases identified in
human beings.